Power shift transmissions are well known in the art. Some power shift transmissions provide shuttle shift capability which permits the vehicle to change direction of operation without requiring the movement of the gearshift lever through each intermediate gear ratio. To accomplish this operation, these known types of shuttle shift transmissions will typically include torque converters. In such transmissions utilizing torque converters for shuttle shifting at high or even moderate speeds, a high energy load is placed on the clutches.
Some power shift transmissions are characterized in that they do not require a different gearshift lever position for each gear ratio which may be selected. While such transmissions have simplified operator control, such transmissions do have drawbacks and lack certain desirable features. For example, these transmissions provide automatic speed ratio matching with no means permitting an operator to intervene manually in the automatic speed ratio matching process.
The operation or response of the transmission clutches vary from one transmission to another, or in a given transmission over a period of time. The present invention alleviates some of these problems and, in addition, provides new methods by which an operator may effect the shuttle shifting process.